Valve control means

Abstract

The invention relates to valve control for an internal combustion engine. The valve control includes a valve, a first camshaft having a first cam member and a second cam member having a different profile from the first cam member and a cam follower assembly for transmitting reciprocating movement to the valve from the cam. The cam follower assembly includes a first cam follower member in engagement with the valve and a second cam follower member movably relative to the first cam follower member, and locking means to enable the follower members to be linked to move together. When the follower members are not linked the valve means is controlled by the first cam follower member in engagement with and following the profile of the first cam member and when the follower members are linked the valve is controlled by the second cam follower member in engagement with and following the profile of the second cam member. One of the cam members having a circular axial cross-section to enable valve deactivation.

We claim: 
     
       1. Valve control means for controlling valve means of an internal combustion engine comprising: cam means comprising a rotatable camshaft having a first cam member and a lobe of circular axial cross-section,   transmitting means for transmitting reciprocating movement to the valve means from said cam means, said transmitting means comprising a first follower member in engagement with said valve means and a second follower member movable relative to said first follower, and   locking means to enable said follower members to be linked so as to move together, wherein   when the follower members are not linked by the locking means the valve means is controlled by the first follower member in engagement with and following the profile of the lobe of circular cross-section and   when the follower members are linked by the locking means the valve means is controlled by the second follower member in engagement with and following the profile of the first cam member and wherein   the second follower member has a bore therethrough and the first follower member is in the form of an inner member located within the bore, said first follower member being movable in the bore relative to the second follower member when the follower members are not linked to move together.   
     
     
       2. Valve control means as claimed in claim 1 wherein the second follower member is generally cylindrical and has a generally cylindrical bore therethrough and the first follower member is a cylindrical member located within the cylindrical bore of the second follower member. 
     
     
       3. Valve control means as claimed in claim 2 wherein the locking means comprises a locking element movable within the second follower member between a first position in which the follower members are not linked and a second position in which the locking element engages a stopped diameter of the first follower member to link the two follower members. 
     
     
       4. Valve control means as claimed in claim 1 wherein the lower edge of only the first follower member directly abuts the top of the controlled valve whereby when the follower members are disconnected the second follower member makes no contact with the valve and transmits no motion thereto. 
     
     
       5. Valve control means as claimed in claim 1 further comprising hydraulic lash adjustment means located between the valve and said first follower member. 
     
     
       6. Valve control means as claimed in claim 1 wherein the first follower member directly abuts the lobe of circular cross-section and the second follower member directly abuts the first cam member. 
     
     
       7. Valve control means as claimed in claim 1 further comprising a third follower member located between said first follower member and said lobe of circular cross-section to provide indirect engagement therebetween. 
     
     
       8. Valve control means as claimed in claim 7 in which said third follower member is held in engagement with said lobe of circular cross-section by spring means. 
     
     
       9. Valve control means as claimed in claim 1 comprising a second cam member on the rotatable camshaft having the same profile as the first cam member and provided on the side of the lobe of circular cross section opposite to the first cam member, wherein the second follower member engages with and follows the profiles of both the first and second cam members. 
     
     
       10. Valve control means as claimed in claim 1 in which actuating means is provided to actuate and de-actuate the locking means for different speeds and loads of the engine. 
     
     
       11. Valve control means as claimed in claim 10 in which the actuating means is manually or automatically operable. 
     
     
       12. Valve control means as claimed in claim 1 in which the first and second follower members are linked at higher engine speeds to improve efficiency of the engine. 
     
     
       13. Valve control means as claimed in claim 1 in which the locking means comprises a locking element movable within said second follower member and held restrained in an unlocked position by spring means. 
     
     
       14. Valve control means as claimed in claim 1 in which the locking means comprises a locking element movable within said second follower member and held restrained in an unlocked position by fluid pressure. 
     
     
       15. Valve control means as claimed in claim 13 in which the locking element has a shaped surface adapted to cooperate with a complementary surface of said first follower member in a locked position. 
     
     
       16. Valve control means as claimed in claim 14 in which the locking element has a shaped surface adapted to cooperate with a complementary surface of said first follower member in a locked position. 
     
     
       17. Valve control means as claimed in claim 14 in which the locking element is moved from a unlocked position to a locked position by means of fluid pressure. 
     
     
       18. Valve control means as claimed in claim 15 in which the locking element is moved from an unlocked position to a locked position by means of fluid pressure. 
     
     
       19. Valve control means as claimed in claim 14 wherein the first follower member has a stepped portion and the locking element engages the stepped portion to link the first and second follower members. 
     
     
       20. Valve control means as claimed in claim 15 wherein the first follower member has a stepped portion and the locking element engages the stepped portion to link the first and second follower members. 
     
     
       21. Valve control means as claimed in claim 1 in which the second follower member is held in engagement with the first cam member by spring means. 
     
     
       22. Valve control means as claimed in claim 1 in which the second follower member is biased toward said first cam member by spring means. 
     
     
       23. Valve control means as claimed in claim 22 in which the spring means holds the second follower member in engagement with the first cam member when the follower members are not linked to move together. 
     
     
       24. Valve control means as claimed in claim 1 in which when the second follower member is linked in engagement with said first follower member there is a gap between said first follower member and the lobe of circular cross-section during the period in which the second follower member engages the lift portion of the first cam member. 
     
     
       25. An internal combustion engine having valve control means as claimed in claim 1. 
     
     
       26. An internal combustion engine having valve control means as claimed in claim 1 wherein the cylinder head of the engine has a bore in which the first and second follower members are located, the second follower member being slidable in the bore relative to the cylinder head.